Thanks a bunch

Locally (Wales, UK) the phrase "thanks a bunch" is used in a sarcastic manner meaning "that wasn't very kind of you". I received an e-mail from an American friend and he used the phrase to mean "Thank you very much". Looking through the bulletin board archives I found it used with both meanings. Are they both correct?

Sure. It all depends on that sarcastic tone of voice. And thanks a bunch for asking.